In a display system, there are two modes for an image engine to output image data to a display screen: a video mode and a command mode. When the video mode is selected, the image engine controls a time sequence of display and a display screen controller displays received image data on the screen. A display screen that supports the command mode, however, has one or more memories. The image engine first writes image data into a memory of the display screen, and the display screen controller reads image data in the memory and provides the read data for the display screen. When image data in a memory of the display screen is updated, an image displayed on the display screen is updated accordingly. When a rate for updating data in a memory, that is, a rate for the image engine to write data into a memory of the display screen, does not match a rate for the display screen controller to read data, tearing occurs on the screen. That is, content of two or more frames is simultaneously displayed on the screen. To achieve matching between a read rate and a write rate, the screen that supports the command mode usually uses an output pin tearing effect (Tearing Effect, TE) signal to indicate current time sequence information of the display screen, such as frame idleness information or row idleness information, to the image engine. In addition, for a display screen that supports a display serial interface (Display Serial Interface, DSI) command mode of the Mobile Industry Processor Interface (Mobile Industry Processor Interface, MIPI) organization, TE information may also be indicated by using an MIPI (Display Command Set, DCS) command. The image engine may determine, according to received TE information, an opportunity for updating a memory of the display screen.
In the prior art, a method for responding to a TE signal includes two modes: a manual mode and an automatic mode. In the manual mode, after 1 is written into a corresponding register TE_MANUAL in an image engine, the image engine transmits image data to a display screen. In this case, an opportunity for configuring the register TE_MANUAL needs to be determined by software. In the automatic mode, after receiving a TE signal, the image engine reads image data from a memory, processes raw image data according to an application requirement, and outputs the processed image data to the display screen through a display interface. In the automatic mode, image data is read from a memory and output only after a TE signal is received, which causes a slow rate for responding to a TE signal. In an extreme case, for example, a valid level of a TE signal sent by the display screen only lasts time of 4 rows, if time for the image engine to read a memory plus time for image processing is larger than the time of 4 rows, a tearing effect may be caused on the display screen. When a TE signal arrives, especially when other data is transmitted on a bus, the image engine obtains image data and processes the image data, which increases an instantaneous bandwidth pressure on the bus used for data transmission. In addition, only two response modes, manual and automatic, exist. In the automatic mode, the image engine responds to all TE signals. In this way, for a specific scenario where a requirement for a refresh frame rate is not high, power consumption is quite high and a performance waste exists; if the manual mode is used to reduce an output frame rate, software intervention, such as interrupt processing, is required, and therefore efficiency is low.